Stabilization of propiolactiones



United States Patent 3,392,174 STABILIZATION OF PROPIOLACTONES GaryPlant Hildebrmd, Wilmington, Del., assignor to E. I. du Pont de Nemoursand Company, Wilmington, Del.,

3,392,174 Patented July 9, 1968 In the production of pivalolactone fromchloropivalic a corporation of Delaware 5 acid, it is necessary toseparate the lactone from the un- NO Drawing- Filed y 31, 1966, 553,702reacted starting material, carboxylic acid by-products, and

6 Claimsother impurities. This separation is accomplished bydistillation; however, the lactone recovery during this distilla- Thisinvention relates to the stabilization of propiolaction is dependentupon the amount and type of impurities tones during their manufaoml'oand Storago by f 10 from which it has to be separated. To illustratethis point, ing h r in a Small amount of Phosphorous and or an in acontrol run, pivalolactone is heated at 100 C. in aqueous Solutionthereofthe presence of these acidic by-products and impurities inPivalolactone and chloropivalolactone are useful for a stainless Steelcontainer The mixture contains 14 conversion to polyesters bypolymerization processes of pivalolactohe and 3,8 of impurities of whichknown in the art. These polyesters can be used to make 15 1 2 moles arecarboxyhc acich periodic ana1yses f fibers and molding rosinsthe mixturereveals that in 5 hours, 18 percent of the The l ct n s HSBd make thesefiber-forming rooms pivalolactone present has polymerized to a highermolecgenerally are stored and refined before they can be used. at Weightmaterial This has been a problem since the propiolactones tend to Therun is repeated using an identical quantity f f dimers, tfimefs and lowPolymers and hence, gel o 20 pivalolactone and impurities except for theaddition of standing, as in storage before their use. This tendency 1s010 of 30 percent aqueOus phosphorous id, Th i grea ly magnified illrefining, which involves dlstinatlonture is maintained at 100 C. in astainless steel container. The heat for distillation accelerates thepolymerization of periodic analyses indicate that ft 5 hours, only 1 thepropiolaotonescent of the pivalolactone present has polymerized to Ithas now been found that the incorporation of small higher molecularWeight i p amounts of phosphorous acid or an aqueous solution v thereofin the propiolactones significantly reduces this EAamPle HIpolymerization tendency during the storage and distilla- This exampleillustrates the stabilizing influence of tion periods normallyencountered. phosphorous acid on an actual distillation.

Generally, it has been found that from 0.01 to 2.0 per- The distillationis a batch operation employing pot cent by weight as based on thepropiolactone of phostemperatures ranging from ambient to 130 C. and ahead phorous acid adequately stabilizes the propiolactones at pressurefrom 100 to 5 mm. of Hg over a 12 hour period. temperatures up to about150 C., which is adequate for The feed material and the amount ofmaterial obtained either storage or refining operations. are reported inTable I.

TABLE I Feed to Recovered Change, Compound Still, lbs From Still, lbs.

Pivalolactone 139. 2 115. 8 23. 4 Chloropivalic acid 7. 6 0.8 6. 6ClCH2C(CHa)2COOCH2C(CH3)2COOH 16.7 8.6 -8.1cioHgcwHmooooHztxofimooooHgc(CHihOOOH. 9. 7 18. 0 +8.3 High molecularweight material Nil 36. 2 +36. 2

The pivalolactonc loss to higher molecular weight material was found tobe 17 percent.

It has been observed that the presence of water has a synergistic effecton stabilization. Generally, when water is to be used, the phosphorousacid is added as a 30 to percent by weight aqueous solution. Hence thewater This distillation is repeated using the same conditions with theaddition of 3.0 pounds of 40 percent aqueous phosphorous acid. The feedmaterials and the materials obtained from this distillation are reportedin Table II.

TABLE II Feed to Recovered Change, Compound Still, lbs. Froir Still,lbs.

Pivalolactone 135. 4 131. 6 3. 8 Chloropivalic acid 7. 3 8. 7 +1. 4ClCI'IzC(CH3)2COOCH2C CH3)2COO 16.3 15.6 0.7 C1CH2C(CII3)2COOCH2C CH3ZCOOCH C(CH3) 8.2 9.8 +1.6 High molecular weight material Nil 3. 4 +3. 4

The pivalolactone loss to higher molecular weight material was found tobe 3 percent. Hence, the phosphorous acid decreased the prvalolactoneloss by a factor of about 5.

is present in an amount of from 1:1 to 70:30 as based on the phosphorousacid.

The following examples are illustrative of the invention.

Example I Example IV As a control, a 10 gram sample ofchloropivalolactone is placed in an open glass test tube which isimmersed in an oil bath maintained at C. Within 5 minutes,polymerization can be observed to begin and the entire contents of thetube are polymerized in 6 hours.

A 10 gram sample of chloropivalolactone to which 0.87 percentphosphorous acid has been added is placed in an open glass test tubewhich is immersed in an oil bath maintained at 100 C. No polymerizationis observed after 6 hours and about 10 percent of the material remainsunpolymerized after two days.

Another 10 gram sample of chloropivalolactone to which 1.2 percent of 30percent aqueous phosphorous acid has been added is placed in an openglass test tube which is immersed in an oil bath maintained at 100 C. Nopolymerization is observed after 22 hours and about 30 percent of thematerial remains unpolymerized after three days.

I claim:

1. A composition consisting essentially of a propiolactone and from 0.01to 2.0 percent as based on said propiolact-one of phosphorous acid.

' 2. The composition of claim 1 which contains water in an amount offrom 1:1 to 7:3 as based on the phosphorous acid.

3. The composition of claim 1 wherein the propiolactone ispivalolactone.

4. The composition of claim 1 wherein the 'pro'piola'ctone ischloropivalolactone.

5. The composition of claim 2 wherein tone is pivalolactone.

6. The composition of claim 2 wherein the propiolactone ischloropivalolactone.

the propiolac- References Cited 7 UNITED STATES PATENTS 3,227,730 1/1966Goldsmith et a1 26 0-343 NICHOLAS S. RIZZO, Primary Examiner.

F. A. MIKA, Assistant Examiner.

1. A COMPOSITION CONSISTING ESSENTIALLY OF A PROPIOLACTONE AND FROM 0.01TO 2.0 PERCENT AS BASED ON SAID PROPIOLACTONE OF PHOSPHOROUS ACID.